No raise in 3 years...HELP!?

I have been working in a restaurant for 3 years. When I started out, I was making $5.15 as a hostess. By law, the minimum wage in GA was raised to $6.55 earlier this year. I recently found out that a girl who has only been at my job for 3 months got a $2 raise to $8.50 an hour, and I am still making minimum wage, after 3 years! Not only is it ludicrous, but I can't talk to my manager because he makes himself completely unavailable and is very mean. My other manager brought up in a manager meeting that I should get a raise and my GM immediately shot it down, saying that I don't do all of the steps(talking to the guests on the way to the table, talking about the soup of the day, etc), but that is a total lie! He then went on to say that the other girl does and that's why she got a raise. But she doesn't do all the steps all the time either. This manager is known for showing extreme favoritism to some, and not speaking at all to many others. This is only a small piece of the picture. He is also fudging numbers(so he looks good to his OD), terminating people out of the system weeks after they should be so his turnover looks good, changing peoples hours from pm to am so he will hit his labor, putting people he doesn't like on 1 day a week with no explanation, etc. He is also best buddies with the OD, and some people that have gone to the OD about him have been treated differently once he finds out.